BRIGHTON, England -- Paul Pogba admitted his "attitude wasn't right" in Manchester United's defeat at Brighton, while United manager Jose Mourinho side-stepped a question about whether his team were capable of challenging for the title this season.

United were woeful as they fell to a 3-2 loss at the Amex Stadium on Sunday, a scoreline that flattered Mourinho's side.

Brighton were 3-1 ahead at half-time and frustrated United until Pogba converted a penalty in stoppage time, and the France international suggested he had not been mentally prepared.

"They had more hunger than us," he told Sky Sports. "I put myself first, that my attitude wasn't right enough. We made mistakes we shouldn't make.

"We were playing at home last week [a 2-1 win over Leicester] and that's different. Different teams, different tactics. I know you cannot always play very, very good. The attitude always has to be very good and we missed that."

Asked at his news conference whether he expected United to challenge Manchester City and Liverpool this season, Mourinho appeared downbeat about their chances.

"At the end of November, December you will have an idea if we can compete," he said.

The Brighton result came on the back of a series of warnings from Mourinho about how tough his team could find this season after a summer that saw them miss out on key transfer targets, particularly a right winger and a centre-back.

But he refused to blame the result on an underwhelming transfer window despite watching centre-backs Victor Lindelof and Eric Bailly make key mistakes following a summer during which he had wanted another central defender.

"I am not going to speak about the market," he said. "We made mistakes and were punished by our mistakes. Sometimes you make mistakes and are punished, sometimes the opponent doesn't take advantage of the gifts, and sometimes they do and this time was almost three on three so they were critical in the gifts that we gave them and because of that I think they deserve [to win].

"Every person in every job [who] makes a mistake is not happy, self-esteem goes down a little bit more, confidence levels -- that's human nature so, if you ask me if my players are in this moment happy, I don't think they are."